The centre of the Milky Way

Dr. Mattia Sormani
University of Insubria (Como, Italy)

I will give an introduction to the structure and dynamics of the central 3 kpc of the Milky Way. The Galactic bar efficiently drives gas from the Galactic disc towards the centre at a rate of ~0.8 Msun/yr, creating a ring-like accumulation of molecular gas at a radius of R=120pc known as the Central Molecular Zone (CMZ). The CMZ is the Milky Way analogue of the star-forming nuclear rings commonly observed at the centre of external barred galaxies, and its formation is governed by a dynamical process similar to that responsible for creating gaps in Saturn's rings. Once in the CMZ ring, approximately 10% of the gas is converted into stars by intense star formation activity. Over Gyr timescales, this activity builds up a flattened stellar system known as the nuclear stellar disc (NSD), which currently has a mass of 10^9 Msun and dominates the gravitational potential of the Milky Way at 30pc<R<300pc. Most of the remaining gas is ejected perpendicularly to the plane by a Galactic outflow powered either by stellar feedback and/or AGN activity. A small fraction continues moving radially inwards, feeding the circum-nuclear disc (CND) at radii of few pc and contributing to the in-situ growth of the nuclear star cluster (NSC). Only a tiny fraction eventually enters the sphere of influence of the central black hole SgrA* at R<1pc.

Conference Hall (2nd floor/ Research and Administration Building A),　Via Zoom